Epidural analgesia for labor pain is not associated with a decreased frequency of uterine activity

Concerned topics of epidural labor analgesia: labor elongation and maternal pyrexia: a systematic review

Objective:

Labor is a complex process and labor pain presents challenges for analgesia. Epidural analgesia (EA) has a well-known analgesic effect and is commonly used during labor. This review summarized frequently encountered and controversial problems surrounding EA during labor, including the labor process and maternal intrapartum fever, to build knowledge in this area.

Data sources:

We searched for relevant articles published up to 2019 in PubMed using a range of search terms (eg, “labor pain,” “epidural,” “analgesia,” “labor process,” “maternal pyrexia,” “intrapartum fever”).

Study selection:

The search returned 835 articles, including randomized control trials, retrospective cohort studies, observational studies, and reviews. The articles were screened by title, abstract, and then full-text, with a sample independently screened by two authors. Thirty-eight articles were included in our final analysis; 20 articles concerned the labor process and 18 reported on maternal pyrexia during EA.

Results:

Four classic prospective studies including 14,326 participants compared early and delayed initiation of EA by the incidence of cesarean delivery. Early initiation following an analgesia request was preferred. However, it was controversial whether continuous use of EA in the second stage of labor induced adverse maternal and neonatal outcomes due to changes in analgesic and epidural infusion regimens. There was a high incidence of maternal pyrexia in women receiving EA and women with placental inflammation or histologic chorioamnionitis compared with those receiving systemic opioids.

Conclusions:

Early EA (cervical dilation ≥1 cm) does not increase the risk for cesarean section. Continuous epidural application of low doses of analgesics and programmed intermittent epidural bolus do not prolong second-stage labor duration or impact maternal and neonatal outcomes. The association between EA and maternal pyrexia remains controversial, but pyrexia is more common with EA than without. A non-infectious inflammatory process is an accepted mechanism of epidural-related maternal fever.

Curative effect of remifentanil on labor analgesia in newborns

Objective: To investigate the curative effect of remifentanil on analgesia in newborns.Patients and methods: One hundred and twenty full-term puerperae from January 2013 to December 2013 were selected and randomly divided into three groups: remifentanil patient-controlled intravenous labor analgesia group (Group A, n = 40), patient-controlled epidural analgesia (PCEA) group (Group B, n = 40), and spontaneous labor group (Group C, n = 40). General conditions, visual analogue scale (VAS) score, labor stage, bleeding, delivery mode, neonatal asphyxia rate, oxyhemoglobin saturation in puerpera, and umbilical arterial blood gas analysis indexes of the fetus were measured. In addition, complications and adverse reactions were recorded.Results: VAS scores in Group A and B were significantly lower than that in Group C at each time point after analgesic intervention (p < .05), without differences at 30 min and 1 h after analgesia between Group A and B (p > .05). However, VAS scores in Group A were significantly higher than those in Group B at the full opening of the uterine orifice and fetal delivery (p < .05). The active phases in the first stage of labor in Group A and B were significantly shorter than that in Group C (p <.05). There were no significant differences in general conditions, VAS score before analgesia, the second and third stages of labor, delivery mode, bleeding, neonatal asphyxia rate, oxyhemoglobin saturation, pH value, partial pressure of oxygen (PO₂), and partial pressure of carbon dioxide (PCO₂) among three groups (p > .05).Conclusions: Remifentanil intravenous labor analgesia is not superior to PCEA, but does not increase adverse effects, suggesting it might be a supplementary method of PCEA.

Plasma oxytocin levels in women during labor with or without epidural analgesia: a prospective study

BACKGROUND

Epidural analgesia (EDA) has been reported to prolong labor. Whether this is by interference with endogenous oxytocin release or other mechanisms is unclear. With increasing numbers of women receiving an EDA, it is important to study its effects on labor. The aim was to study the concentration of plasma oxytocin and the progress of labor in women with and without EDA.

METHODS

Thirty-four full-term women in spontaneous labor were included, 17 with epidural and 17 controls, matched for cervical dilatation and parity. Oxytocin was measured by radioimmunoassay before analgesia, 60 min later and after placental discharge. No oxytocin augmentation was given during the first hour.

RESULTS

EDA during labor was associated with a fall in plasma oxytocin. There was no difference in plasma oxytocin levels between the groups at inclusion. One hour later, oxytocin concentrations had decreased in the epidural and increased in the control group (Student's t-test, p = 0049). The change in oxytocin levels between the first and second sample differed significantly between the groups (ancova, p = 0.028). No difference in cervix dilatation between the groups 1 h after inclusion was noted, but women with EDA had a longer labor compared with those without, especially those with epidural and oxytocin augmentation during the later phase of the first stage of labor.

CONCLUSION

EDA during labor may interfere with the release of plasma oxytocin, which may be one mechanism behind prolongation of labor. Larger studies are needed to clarify the effects of epidural analgesia and the role of oxytocin during labor.

Epidural analgesia does not prolong the third stage of labour

PURPOSE

To investigate whether there is an association between epidural analgesia and duration of third stage of labour, and between epidural analgesia and type of placental delivery (spontaneous vs expressed vs manual).

METHODS

We examined, retrospectively, the computerized labour and delivery data of all 7,468 parturients who had vaginal deliveries from 1996 to 1999 at the Civic Campus of the Ottawa Hospital.

RESULTS

There was no difference in duration of third stage of labour between women with and without epidural pain relief who had spontaneous or expressed (fundal pressure/gentle cord traction) placental delivery. Duration of third stage of labour was shorter in women with epidural analgesia requiring manual removal of placenta. (25.3 min vs 40.1 min, P < 0.0001). The incidence of expressed placental delivery or manual removal of placenta was not different between the groups.

CONCLUSIONS

We conclude that there is no clinically important difference in duration of third stage of labour between women with or without epidural analgesia who have spontaneous placental delivery or placental expulsion with fundal pressure/gentle cord traction. However, duration of third stage of labour was shorter in women who received epidural analgesia and required manual removal of the placenta.

The effects of opioids on isolated human pregnant uterine muscles

We determined the effects of fentanyl, sufentanil, morphine, and meperidine on the spontaneous contractility of isolated human pregnant uterine muscle strips. Uterine specimens were obtained from normal full-term parturients undergoing elective lower-segment cesarean delivery. Longitudinal muscle strips were prepared and mounted vertically in tissue chambers to record their isometric tension. Opioid concentration-response curves were constructed after rhythmic contractions were established. The responses were also examined in the presence of opioid receptor blocker, nitric oxide synthase inhibitor, beta-adrenoceptor blocker, or cyclooxygenase inhibitor. Fentanyl and meperidine inhibited uterine contractility in a concentration-dependent manner, their concentration that inhibited 50% being 2.3 x 10(-6) and 1.0 x 10(-3)M, respectively. Sufentanil and morphine had no significant effects on uterine contractility. Pretreatment with either naloxone, N(G)-nitro-L-arginine methyl ester, atenolol, or indomethacin did not affect the uterine responses to opioids. These results demonstrate that fentanyl and meperidine may have direct inhibitory effects on the contractility of the human uterus, though at supraclinical concentrations.

IMPLICATIONS

Opioids do not have a significant effect on spontaneous contractions of gravid human uterine muscle at their clinically relevant concentrations.